The actor, who worked with Savage on “Gossip Girl” and was a series regular on “Dexter,” will play the competitive and steely Alan Shepard, one of the first astronauts in space. Despite a playboy reputation, Shepard and his wife Louise were married for 53 years.

Harrington joins a femme-heavy cast that includes JoAnna Garcia, Azure Parsons, Zoe Boyle and Odette Annable — although the part of his wife has not been cast.

The 10-episode miniseries, which is set to bow this summer, is exec produced for ABC Studios by writer Savage and Josh Schwartz and Len Goldstein through their Fake Empire shingle, as well as Michael London and Janice Williams for Groundswell. It’s based on Lily Koppel’s book with the same name. The pilot is directed by “The Notebook’s” Nick Cassavetes.